1. Field of Invention
The present invention relates to a display control apparatus such as an LCD driver IC that controls display of a display apparatus such as an LCD (Liquid Crystal Display), and to an electronic appliance that is equipped with such a display control apparatus.
2. Description of Related Art
In general, as shown in FIG. 6 for example, an LCD driver which controls the display of an LCD (not shown) has a plurality of memory cells MS, each being composed of a two-port memory, disposed in a manner corresponding to a dot matrix of the LCD. The memory cell MS has, for example, two inverters I1 and I2, two transistors T1 and T2 for data writing via a first port, and a three-state inverter I3 for data reading via a second port. Display data for the LCD from a controller 10 is written in the memory cells MS. The three-state inverter I3 is controlled according to a timing signal from a timing signal generation circuit 12 to successively read out data stored in the memory cells MS and output the data through a buffer BF from a segment terminal to the LCD.
When the LCD driver is shipped out from the factory, an operation test for the LCD driver is conducted. For confirmation of the operation of the LCD driver, display data as well as prescribed test data are written in each of the memory cells MS, the stored data is successively read out from the memory cells MS through the second ports, and the data is retrieved and observed by a test probe that is connected to the segment terminal.
In general, data from the controller 10 is written in the memory cells MS by designating addresses of the memory cells MS through a bus. Normally, the bus is generally a four-bit bus or an eight-bit bus, and therefore, the number of the memory, cells that can be written with one writing operation is limited. Accordingly, writing operations need to be repeated in order to write the data in the entire memory cells MS. Such operations may be enough to meet the requirements of the user and thus may not present any problem, after the LCD driver is shipped out and used by the user. However, during the operation test to be conducted before shipping out, it may take a substantial amount of time just to perform an operation to write test data in the memory cells MS, thereby obstructing the effort to shorten the time for the test.
Also, typically, a test pattern is created through performing a logic simulation and confirming its operation. Therefore, there may be problems in that it may take a substantial amount of time to create a test pattern to be written in the entire memory cells MS, since such test pattern amounts to a substantial length. It also may take an enormous amount of time to perform the logic simulation.
It is an object of the present invention to at least provide a display control apparatus, such as an LCD driver and the like, that can shorten the time required for its operational tests and to provide an electronic appliance that is equipped with the display control apparatus.
A display control apparatus in accordance with an exemplary embodiment of the present invention may consist of a storage region composed of a two-port memory in which display data is written via a first port and the display data is read via a second port, and outputted through a display apparatus terminal to a display apparatus. In the display control apparatus of this exemplary embodiment, the display apparatus terminal is structured to be able to switch between a state for data input and a state for data output. Data-writing in the storage region through the second port and data-reading from the storage region through the second port can be mutually switched. Data to be inputted in the display apparatus terminal can be written in the storage region via the second port.
In the exemplary embodiment of the present invention set forth above, display data is written in the memory region composed of a two-port memory, and the data in the storage section is read via the second port, and outputted from the display apparatus terminal to a display apparatus such as an LCD. In this exemplary embodiment, the display control apparatus is structured such that the display apparatus terminal can be switched between a state for data input and a state for data output, data-writing in the storage region through the second port and data-reading from the storage region through the second port can be switched with one another, and data to be inputted in the display apparatus terminal can be written in the storage region via the second port.
It is noted that data for a display control apparatus for an LCD or the like is written in a storage region such as a RAM through a bus. In this case, the storage region that can be written with one writing operation is limited. Accordingly, writing operations need to be repeated in order to write the data in the entire storage region. Such operations may not present any problem when the display control apparatus is operated under a normal use condition. However, during the operation test to be conducted before shipping out, it may take a substantial amount of time just to write the test data in the storage region.
However, the display apparatus terminal is switched to a state that allows data input, and the second port is switched to a state that allows data-writing through the second port to the storage region, to thereby switch to a state that allows writing input data to the display apparatus terminal into the storage region. As a result, under the above-described condition, when test data is inputted in the display apparatus terminal, the test data is written in the storage region. As a consequence, the test data is written in the storage region in the unit of the number of the display apparatus terminals. This may shorten the time for writing test data in the storage region compared to the case in which test data is written in the storage region through a bus, and thus may shorten the processing time required for the test.
In another exemplary embodiment, in the display control apparatus, the storage region may consist of a plurality of memory cells, and data can be written in each of the memory cells via the single display apparatus terminal.
In the display control apparatus of this exemplary embodiment, data can be written in each of the plurality of the memory cells via the single display apparatus terminal. As a result, the display apparatus terminal does not need to be provided in each of the memory cells.
In another exemplary embodiment, in the display control apparatus, a plurality of the display apparatus terminals are provided.
In the display control apparatus of this exemplary embodiment, the plurality of display apparatus terminals are provided and data are written through the plurality of display apparatus terminals. Accordingly, data can be simultaneously written in the plurality of memory cells that compose the storage region.
In another exemplary embodiment, the display control apparatus is used as a display control apparatus for an electronic appliance.
Furthermore, an electronic appliance in accordance with an exemplary embodiment of the present invention is equipped with the display control apparatus according to the various exemplary embodiments discussed above.